There are various types of apparatus for continuously washing a fabric such as a woven or knitted fabric in an opened form, with water. However, some of the conventional types of washing apparatuses are not satisfactory in that the apparatus has a relatively small washing capacity in spite of its relatively large scale and a relatively poor washing efficiency in spite of its relatively large consumption of washing water.
In order to eliminate the above-mentioned disadvantages, attempts have been made to assemble a plurality of washing units in a vertical multi-stage form. Each washing unit comprises a vessel for containing washing water, a dipping roll for introducing a fabric to be washed into the vessel and a guide roll for withdrawing the fabric from the vessel and forwarding the withdrawn fabric toward the next upper washing unit. Fresh washing water is supplied to a vessel in an uppermost washing unit, and the washing water is subsequently flowed down to a vessel in a next lower washing unit. This type of washing apparatus has an enlarged washing capacity in spite of its relatively small scale and an increased washing efficiency in spite of its relatively small consumption of washing water. However, this type of washing apparatus has the following disadvantages. Usually, in the conventional multi-stage type of washing apparatus, a fabric is withdrawn from the washing vessel and, then, forwarded toward the guide roll through a substantially horizontal path. Then, the fabric is forwarded from the guide roll to a dipping roll in a next upper washing vessel through an upwardly sloping or substantially horizontal path. When the fabric is withdrawn from the washing vessel, a considerable amount of washing water accompanies the fabric.
While the fabric accompanied by the washing water travels along a horizontal path, both selvadges of the fabric are tightened whereas the middle portion of the fabric entirely or locally sags due to the weight of the accompanying washing water, so that the fabric which in a normal condition is in an opened flat form becomes convex in form. Accordingly, the accompanying washing water is collected in the convex-shaped portion of the fabric. Then, the collected washing water overflows from the convex-shaped portion over one of the selvadges of the fabric. This overflow causes the fabric to be tipped from side to side, and almost all of the washing water collected in the convex-shaped portion flows down from the fabric. During the continuous washing operation, the above-mentioned phenomena are frequently repeated. The tipping motion of the fabric results in fluctuations of the tension applied to the opened fabric. This fluctuation of tension in turn results in undesirable formation of wrinkles in the fabric, irregular bending of weft yarns in the fabric and local alternation in the density of the weft yarns in the fabric. These undesirable phenomena frequently occur, especially, in the case of thin woven fabric and result in a decrease in the quality of the washed fabric.
In order to prevent the above-mentioned undesired phenomena which occur in the conventional type washing apparatus, an additional guide roll or bar is located in a middle portion of each horizontal path of the fabric, or the guide roll is located in a location relatively close to the washing vessel. In the former case, the additional roll or bar in each washing unit is effective for preventing the deformation of the opend fabric into the convex form and the formation of wrinkles in the fabric. However, the arrangement of a number of the additional rolls or bars in the washing apparatus results in difficulty in operations inside the washing apparatus, that is, causes the inside of the washing apparatus to be difficult to clean and, further, makes it difficult to initially arrange the fabric among the several rolls and bars along a predetermined fabric path. Also, in the latter case, the location of the guide rolls close to the washing vessel results in a shortened fabric path which causes the washing efficiency of the apparatus to be poor.
In the conventional multi-stage type washing apparatus, the fabric usually approaches the washing vessel upwardly or substantially horizontally from a guide roll. In this case, at least one additional guide roll should be arranged in or above the washing vessel for turning the direction of the moving fabric downward. Accordingly, even if two rolls are located in the washing vessel, one of the rolls is merely utilized as a turning guide roll which is not effective for immersing the fabric in the washing water in the vessel. That is, this guide roll is not effective for enhancing the washing efficiency of the multi-stage type washing apparatus. In order to utilize the above-mentioned two rolls as real dipping rolls for immersing the fabric in the washing water, it is necessary to arrange an additional guide roll or bar above each dipping roll. This additional guide roll or bar causes the washing apparatus to be complicated and to be significantly enlarged.
Under the above-mentioned circumstances, in the conventional multi-stage type washing apparatus, the fabric is allowed to be immersed only once in the washing water in each washing vessel. Accordingly, the washing efficiency of the conventional multi-stage washing apparatus is unsatisfactory.